Oscillograph apparatus



June 24, 1941. H, N. WAGAR OSCILLOGRAPH APPARATUS mea nay 1s. 19351 JUVE/SNUR BV HA@ man@ sharply on the record sheet.

Patented June 24, 1941 OSCILLOGRAPH APPARATUS Harold N. Wagar, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application May 13, 1939, Serial No. 273,591

Claims.

This invention relates to recording devices and more particularly to string galvanometer oscillographs for making records of rapidly` changing physical phenomena.

In the development of electromechanical apparatus it is very helpful if the actual mechanical response thereof to electrical energy changes are fully known. Heretofore those skilled in the art have constructed oscillographs having a plurality Aoi! electroresponsive recordingr elements adapted to record a plurality of electrical phenomena simultaneously on a single moving record sheet. Examples of this type of apparatus are disclosed in U. S. Patents 1,871,361, granted August 9, 1932, and 1,958,611, granted May l5, 1934, and in Bell laboratories Record, September 1937, page 26. In these patents all the movable galvanometer recording elements are parallel, they move in the same direction and are in substantially the same place so that the images of their shadows appear Oscillographs are normally so constructed that their galvanometer recording elements move transversely to the motion of their record sheets as it is evident from the nature of their structure that all components of motion appearing at the record strip to move in the same direction as the record strip are not recorded. However, in studying the actual motion of electromechanical apparatus simultaneously with its related electrical energy changes, it is very seldom ypossible to have these conditions met. The movable parts of associated electromechanical apparatus are seldom so positioned that the motions thereof readily appear transverse to the motion of the record strip unless special optical apparatus is employed.

It is accordingly an object of this invention to provide a suitable optical system in combination with a recording device whereby continuous records may be made of the mechanical movements of an electromechanical apparatus irrespective of their angular directions with respect 'to the record strip.

It is a further object of this invention to provide a means whereby these records may be made simultaneous with their related electrical phenomena.

The foregoing objects are attained by providing in combination with a recording device of the oscillograph type an optical adjusting means adapted to orient the directions of motion of the recording images at the record strip so that they move transversely to the direction of motion of said strip.

The invention may be more particularly described in connection with vthe accompanying drawing in which:

Fig. 1 illustrates the optical inverting eiiect of a trapezoidal prism;

Fig. 2 illustrates the optical rotating or orienting property of the prism of Fig. 1;

Fig. 3 discloses a particular embodiment oi the invention;

Fig. 3A is a portion of Fig. 3; and

Fig. 4 is a. portion of a record strip illustrative of the results obtained from a simple application of this invention.

The optical properties of trapezoidal prisms are well known in the optical art but by way of completenessa brief description is given herewith of thel particular properties employed by this invention. In Fig. 1 a trapezoidal prism I is mounted on a handle 2 for convenience of description. The raysfrom an erect object 3 passing through prism I will form an inverted image 4 on a screen or record strip 5. In this figure .the projection of image 4 viewed` from object 3 would be collinear with the object but inverted. However, if the prism is rotated about its principal optical axis through an angle i as shown in Fig. 2 the image will appear to lbe rotated through an angle 2d and in the same direction as the prism. This property of rotation or orientation is employed in this invention to orient the images of angularly displaced movable objects in order to obtain a true and accurate record of the motions thereof.

A specific application of the above-described optical principle is disclosed in Fig. 3 in connection with an oscillograph of the type more particularly described in the aforementioned U. S. Patent. 1,958,611 and in Electronics August 1931, pages and r11. Briefly, however, the record strip handling portion of the oscillograph comprises a supply roll 6 of sensitized paper enclosed in a light-tight compartment (not shown) of conventional design. The strip 5 from roll 6 is run at substantially uniform speed past the printing point 'I where the images are photographically printed. The strip is then passed into a temporary storage chamber 8 and iinally through suitable processing baths 9 and I0 where the photographic record is developed and washed.

The optical system comprises a light source I I, condenser lenses I3, focussing lenses I9, prism 20, projector lenses 2|, prism 22, mask 23 with aperture 23 and cylindrical lens 24. An occulting or timing disc I2 is inserted between light source Il and condenser lenses I3 and its' motion is such as to form parallel spaced timing bars 25 on the record sheet as shown in Fig. 4. 'I'he galvanometer I4 is of the type disclosed in the aforementioned U. S. Patent; 1,871,361 and although only one 'string I5 is used for illustration, it is obvious that more may be used. The image of string I5 is focussed in the plane of contacts I6 and is oriented by prism 20 so that it is parallel with the length of contacts I6, as indicated by dotted line I5', whereby its direction of motion is the same as .the direction of motion of contacts I6. For a specilc illustration of the invention contacts I6 are shown to be operated by coil I6' in series with 'battery I8, switch I'I andl galvanometer string I5.

The rotated image I5' of string I5 and the image of contacts I6 are Afocussed on an apertured screen 23 by projector lenses 2| `and are oriented by prism 22 so that their apparent directions of motion at the screenlre' all transverse to the direction of motion of the record strip 5. It is to b e understood that masking screen 23 is actually very close and parallel with record strip 5 and is shown extended therefrom in Fig. 3 only for the sake of clarity. Cylindrical lens 24 also is of relatively small dimensions and consequently occupies very little space. Its purpose is to concentrate the light emerging from aperture 23 into a narrow line transversely across record strip 5 and at the printing line 'I.

The height, that is to say the narrow dimen'- sion of Vaperture 23', is made adjustable by any `convenient means, not shown. lThis adjustment is desirable for this particular disclosure in order to mask out unwanted light from above andbelow the margin of the contact points. This is better shown in Fig. 3A where the imagesof the contacts I6" and the galvanometer string I5" are shown viewed from the record strip side, the dotted portion representing the masked areas. Now if the aperture height is increased as indicated by the dotted rectangle, a light space 26 will be unmasked to register on the record strip thereby rendering Ait a little more difficult to read. The specific form of mask and the shape of the open space thereof will depend upon the type of .oscillographused and upon the conliguration of the mechanical structure observed. The cylindrical lens 24 compresses the emergent light from aperture 23' into a narrow line as previously stated.

In order to more easily observe the vibratory action of objects in contact, particularly where one of them is very large, it is frequently found desirable to depart from complete masking as above described by increasing the height of the aperture just enough to allow a small light leak through space 2.v It is evident lthat `this will form a narrow light trace between the shadows of the two contacting objects, the shape of which corresponds with their vibratory motion. In the specific case of the relay contact herein disclosed, this trace may manifest itself in two ways. First, if the width of the trace momentarily increases this indicates that there is a relative motion between the two contact springs commonly called contact chatter or rebound and, second, the wavy form of the trace indicates the magnitude and direction of the en masse vibratory rno tion of the closed contacts.

Fig. 4 discloses a portion or" a record. strip which may be obtained from studying the action of a particular pair of relay contacts such as I6 of Fig. 3. The traces-are actually caused by compressed shadowl images ci small portionspo the galvanometer string relay contacts.

Lines 25 are the timing lines produced by occulting disc I2. The meaning of such an oscillogram is at once obvious to anyone skilled in this art and requires no further description.

In using the above-described apparatus to observe the action of relay contacts I6 simultaneously with their associated electrical lphenomena the contacts are inserted into the optical path between .prism 20 and projector lens 2|, as shown. It is immaterial what angle they assume so long as they operate in a plane substantially parallel with record strip 5. Projector lenses 2| are then adjusted to bring the shadow images I6" of the contacts in focus at strip 5 and consequently substantially in focus on the mask 23. Since the actual motion of contact I6 may be at any arbitrary angle, prism 22 isrotated to orient the motion of their images transverse to the record strip as seen on mask 23. The height of the aperture is then adjusted to mask out any unwanted light, in this case that appearing around the margins of the contact points as previously described.

Focussing lenses I9 are then adjusted to bring the shadow image I5" of string I5 into sharp focus at strip 5. This will occur when a real image I5' is formed in the plane of the contacts I6 in a manner well known. However, since prism 22 was rotated, the nal image I5" also suiered rotation but is not necessarily in the required position at aperture 23', with its motion transverse to that of record strip 5. Prism 20 is rotated to orient iinal image I5" into the correct position.

It is obvious that a plurality of stringsA could be used so that for example a second string could record the current through or voltage across contacts I6 and a third string the voltage or currentchanges in some other electrically related or even unrelated circuit. Moreover, any electromechanical system having a movable part capable of insertion in the optical system may be substituted for the speciiic contacts herein disclosed for illustrative purposes.

What is claimed is:

l. In a recording device having a light sensigalvanometer, a movable element therefor responsive to an electric phenomenon, a mechanically movable body the motion whereof is operatively related to said phenomenon and which is movable in a plane parallel to said record strip and at any iixed angle with respect to its direction of motion, optical means adapted to transmit images of said movable element and said body to said record strip, and optical adjusting means adapted to orient the direction of motion of said images into a line transverse to the motion of said record strip.

2. In a recording device having a light sensitive record strip moving in a fixed direction, a mechanically movable body movable in a plane substantially parallel to said recorclV strip and at any variable angle with respect to its direction of motion, optical means adapted to transmit an image of said body to said record strip, and optical adjusting means adapted to orient the direction of motion of said image into a line substantially perpendicular to the motion of said record strip.

3. In a recording device having a light sensitive record strip moving in a fixed direction, an oscillograph with at least one movable element responsive to an electric' phencmencn, an optical system for producing an image of said element and for recording any motion thereof on said strip, a mechanical body movable in response to said phenomenon along a xed axis and in a piane substantially parallel with said strip and at any angle with respect vto its direction of motion, an optical projection means interposed in said optical system adapted to record the motion ci' said body on said strip, and means for orienting the direction of motion of said projection into a line substantially transverse to the direction of motion of said strip. 1

4. In a recording device having a iight sensitive record strip moving in a ixed direction, an oscillograph with at least one movable element `responsive to an electric phenomenon, an optical system for producing an image of said element and for recording any motion thereof on said strip, a mechanical body movable in response to said phenomenon along a fixed axis and in a plane substantially parallel with saidV strip and at any angle with respect to its direction of motion, an optical projection means interposed in said optical system adapted to record the motion of said body on said strip. and means for orient-- ing the direction of motion of sf-.id projection into a line substantially transverse to the direction of motion of said strip, said means comprising a trapezoidal prism. y Y

5. In a recording device having a light sensitive record stripv moving in a fixed direction, an osciliograph with at least one movable element responsive to an electric phenomenon, an optical system for producing an image of said element and for recording any motion thereof on said strip, a mechanical body movable in response to said phenomenon alongv ailxe'd axis and in a plane substantially parallel with said strip and at any angle with respect to its direction of motion, an optical projection means interposed in said optical system adapted to record the motion ofgsaid body on said strip, a prism interposed in vsaici optical system for orienting the direction of motion of the image of said oscillograph element so lthat it is in the same direction as the motion of said body and another similar prism also interposed in said system for orienting the direction of motion of both the image of said element and the projection of said body into a line substantially transverse to the direction of motion' oi' said strip.

HAROLD N. WAGAR. 

